The trefoil factor family (TFF) is a group of highly stable peptides, having a three-leaved clover-like structure formed from six cysteine residues. Three TFF peptides (TFF1, TFF2 and TFF3) have been identified so far in humans. TFFs are present in mucus-related tissues such as the alimentary tract, and are secreted mainly by mucus-secreting cells. The expression of TTF peptides is up-regulated in the vicinity of damaged mucosa and in regenerating glands. It is reported that the main functions of TFF peptides lie in the augmentation of cell migration processes (motogenic effects), protection of cells, and suppression of apoptosis [Nature Reviews, Molecular Cell Biology, Vol. 4: 721-732(2003)].
TFF2 is a peptide of 106 amino acid residues, initially isolated from porcine pancreas. The TFF2 peptide is abundant in the gastric mucous neck cells, the pyloric region of the stomach, the mucosa surrounding ulcers, the regenerative mucosa, the overlying mucus layer, Brunner's glands, and so forth.
It has been confirmed with experiments using rats that TFF2 prevents the development of colitis and gastric ulceration and also accelerates the healing thereof [Gastroenterology 108: 108-116(1995); Gastroenterology 110: 489-497(1996); Alim. Pharmacol. Ther., 14: 1033-1040(2000); Gut, 45: 516-522(1999); Gut, 44: 636-642, 1999; and J. Leukoc. Biol., Vol. 75: 214-223(2004)].
Other experiments show that indomethacin-induced gastric ulcers are exacerbated in TFF2 knockout mice [J. Clin. Invest., Vol. 109: 193-204(2002)].
Eur. J. Clin. Invest., 32: 519-527(2002) discloses the ability of TFF2 to stabilize mucus.
Am. J. Respir. Cell Mol. Biol., Vol. 29: 458-464(2003) teaches that TFF2 might be involved in regulating the proliferation of damaged airway epithelia.
It can be understood from the above that TFF2 plays key roles in protection against and repair of mucosal injury. With regard to diseases which are likely to be cured with TFF2, improved therapeutic effects are expected by a promotion of endogenous TFF2 production.
Gastroenterology, 126: 796-808(2004) discloses that TFF3 is effective for curing alimentary tract mucositis such as stomatitis induced by the administration of carcinostatics. Science, Vol. 274: 259-262(1996) and Gastroenterology, 119: 691-698(2000) conclude, from the fact that stomach cancer was developed in TFF1 knockout mice, that the TFF1 gene may function as a tumor suppressor gene. Nature Reviews, Molecular Cell Biology, Vol. 4: 721-732(2003) and Int. J. Mol. Med., 12: 3-9(2003) suggest that TFF2 may act in a similar way as TFF1 and TFF3.
As compounds for up-regulating TFF2 expression, ligands for peroxisome proliferator-activated receptor-γ (PPARγ) (e.g., indomethacin, aspirin, prostaglandin J2 and troglitazone) are known [FEBS Lett., 488: 206-210(2001); Alim. Pharmacol. Ther., 18 (suppl. 1): 119-125(2003); FEBS Lett., 558: 33-38(2004); and Can. Res., 61: 2424-2428(2001)].
Among various proteins, keratinocyte growth factor (KGF) is reported to enhance TFF2 and TFF3 expressions in rat lower gastrointestinal tracts [Am. J. Physiol. Regul. Integr. Comp. Physiol., 284: R564-R573(2003)].
Some studies teach pharmacological actions of the TFF peptides themselves, and suggest the possibility of their application in clinical medicine (WO92/14837, WO02/102403, and WO02/46226).
WO01/002377 and WO02/051419 disclose various compounds having a substituent containing a 2,4-dioxo-thazolidinyl or 4-oxo-2-thioxo-thiazolidinyl moiety on a heteroaryl skeleton such as a quinoline. These documents also disclose that such compounds exhibit telomerase inhibitory activity.